Margit Beck1, Mario Jekle, Thomas Becker. 1. Institute of Brewing and Beverage Technology, Cereal Process Engineering, Freising-Weihenstephan, Germany. margit.beck@wzw.tum.de.
Abstract
BACKGROUND: The rheological properties of wheat dough for yeast-leavened products were tested at different levels of sodium chloride (NaCl) addition ranging from 0 to 40 g NaCl kg⁻¹ wheat flour. Rheological tests carried out to make this evaluation included (1) empirical rheological methods of the Farinograph, load extension and a dough stickiness test and (2) fundamental rheological methods of creep recovery and dynamic rheometry. Modifications to the gluten matrix microstructure by NaCl were examined by confocal laser-scanning microscopy. RESULTS: Highly significant (P⩽0.001) differences due to NaCl addition could be determined in particular by the stickiness test as well as by examination of the creep test with the Burger model. Rheological changes measured in the creep test probably depend on protein charge shielding due to NaCl interaction, resulting in an improvement in gluten network formation. An increase in dough stickiness was measured when using NaCl. CONCLUSION: The present result for stickiness is contrary to the common subjective results. Therefore the theory proposed here for increased stickiness suggests that it is based on more non-protein-bound water in the dough system due to NaCl interaction and thus more viscous dough behaviour, which leads to higher stickiness as measured with the stickiness test. This may also suggest that the objectively measured 'stickiness' in this case does not properly indicate the subjectively measured stickiness it was designed to represent.
BACKGROUND: The rheological properties of wheat dough for yeast-leavened products were tested at different levels of sodium chloride (NaCl) addition ranging from 0 to 40 g NaCl kg⁻¹ wheat flour. Rheological tests carried out to make this evaluation included (1) empirical rheological methods of the Farinograph, load extension and a dough stickiness test and (2) fundamental rheological methods of creep recovery and dynamic rheometry. Modifications to the gluten matrix microstructure by NaCl were examined by confocal laser-scanning microscopy. RESULTS: Highly significant (P⩽0.001) differences due to NaCl addition could be determined in particular by the stickiness test as well as by examination of the creep test with the Burger model. Rheological changes measured in the creep test probably depend on protein charge shielding due to NaCl interaction, resulting in an improvement in gluten network formation. An increase in dough stickiness was measured when using NaCl. CONCLUSION: The present result for stickiness is contrary to the common subjective results. Therefore the theory proposed here for increased stickiness suggests that it is based on more non-protein-bound water in the dough system due to NaCl interaction and thus more viscous dough behaviour, which leads to higher stickiness as measured with the stickiness test. This may also suggest that the objectively measured 'stickiness' in this case does not properly indicate the subjectively measured stickiness it was designed to represent.